Re: What's left over.

Linus Torvalds
2002-11-01T15:19:22Z

In article <20021031194351.GA24676@tapu.f00f.org>,
Chris Wedgwood <cw@f00f.org> wrote:
>On Thu, Oct 31, 2002 at 10:49:10AM -0800, Linus Torvalds wrote:
>
>> Any hardware that needs to go off and think about how to encrypt
>> something sounds like it's so slow as to be unusable. I suspect that
>> anything that is over the PCI bus is already so slow (even if it
>> adds no extra cycles of its own) that you're better off using the
>> CPU for the encryption rather than some external hardware.
>
>Except almost all hardware out there that does this stuff is async to
>some extent...

That's not my argument. I realize that external hardware on a PCI bus
_has_ to be asynchronous, simply because it is so slow.

The question I have is whether such external hardware is even worth it
any more for any standard crypto work. With a regular PCI bus
fundamentally limiting throughput to something like a maximum of 66MB/s
(copy-in and copy-out, and that's so theoretical that it's not even
funny - I'd be surprised if RL throughput copying back and forth over a
PCI bus is more than 25-30MB/s), I suspect that you can do most crypto
faster on the CPU directly these days.

Maybe not. The only numbers I have is the slowness of PCI.

Linus